In recent years, the promotion of environmental protection has become a main issue. Nowadays, the movement aimed at the reduction of carbon emissions has been mushrooming. The electric industry is dedicated to develop green products, such as solar cells and light-emitting diodes. To the end of environment protection and energy saving, the light-emitting diodes have been widely employed in illuminating equipment.
Referring to FIG. 1, which shows the configuration and arrangement of a LED lighting system according to the prior art. As shown in FIG. 1, a plurality of LED lighting devices are placed in different locations in the house depending on user's demands. A single lighting device driver 1 is used to drive the LED lighting devices 1A-1C, thereby driving the LED lighting devices 1A-1C to illuminate for providing enough light for the house. The conventional lighting device driver 1 is implemented by a two-stage power converter, including a first stage circuit 11 and a second-stage circuit 12. The first-stage circuit 11 is an A-DC converter for converting an input voltage Vin into a bus voltage Vbus having a constant voltage value and outputting the bus voltage Vbus to the second-stage circuit 12. The second-stage circuit 12 includes three DC/DC converters 121-123. The output ends of the DC/DC converters 121-123 are respectively connected to a set of lighting device connection base (131A, 131B), (132A, 132B), (133A, 133B). The lighting device connection base sets (131A, 131B), (132A, 132B), (133A, 133B) are respectively connected to an LED lighting device for respectively transmitting a lamp voltage Vo1, Vo2, Vo3 to a corresponding LED lighting device 1A-1C.
When the fitting switch 10 is turned on, the input voltage Vin is transmitted to the input terminal of the first-stage circuit 11 through the fitting switch 10, and is converted into a bus voltage Vbus having a constant voltage value of 52V by the first-stage circuit 11. The bus voltage Vbus is downshifted into lamp voltages Vo1, Vo2, Vo3 respectively by the DC/DC converters 121-123. In this example, the lighting device driver 1 is configured to drive the LED lighting device with the same specification. In order to allow each LED lighting device to have the same luminance, the specifications of the DC/DC converters 121-123 must be the same to allow the lamp voltage Vo1, Vo2, Vo3 to be 50V. Also, the DC/DC converters 121-123 must respectively provide lamp currents Io1, Io2, Io3 having the same current value with each other. Nonetheless, the DC/DC converters 121-123 have difference performance as the manufacturing processes of the DC/DC converters 121-123 are different and their constituent elements have tolerances. Therefore, the lamp currents Io1, Io2, Io3 outputted by the DC/DC converters 121-123 are not the same.
Also, as each circuit stage has power loss, the input energy will diminish by the conversion process of the first-stage circuit 11 and the conversion process of the second-stage circuit 12. Thus, the energy transmitted to the lighting device is reduced. This will deteriorate the power efficiency and waste electric energy. More disadvantageously, the operating efficiency of the lighting device driver 1 can not be promoted. Hence, the goal of reducing the carbon emissions can not be fulfilled. Furthermore, each DC/DC converter has a control circuit for controlling the operations of the DC/DC converter. Thus, the circuit complexity of the DC/DC converters 121-123 is high and the manufacturing cost of the DC/DC converters 121-123 is excessively high. If the number of the lighting device to be driven by the lighting device driver is not equal, for example, when the number of the lighting device to be driven by the lighting device driver is changed from three to six, the circuitry of the lighting device has to be redesigned according to the user's demands as the lighting devices can not be modularized to allow the number of the lighting device in the lighting device module to be changed. This would waste the development time and elevate the manufacturing cost.
Furthermore, the lighting device connection base sets (131A, 131B), (132A, 132B), (133A, 133B) and the contacts a-f of the lighting devices 1A-1C are provided with waterproof structures to meet the requirements of safety regulation. This can prevent the moisture from infiltrating the lighting device driver 1 and the lighting devices 1A-1C and damaging the lighting device driver 1 and the lighting devices 1A-1C accordingly. As each lighting device needs two electric wires pulled out from the lighting device driver 1 to be connected with the lighting device, multiple electric wires needs to be pulled out from the lighting device driver 1 when the lighting device driver 1 is set to drive a plurality of lighting devices. This would require a plurality of waterproof structures and complicate the wiring process. Hence, the construction process will be toughened and the cost incurred with the construction process is increased. Besides, the conventional two-stage lighting device driver 1 respectively provides a lamp voltage Vo1, Vo2, Vo3 having a lower voltage value to each lighting device 1A-1C. When the conventional two-stage lighting device driver 1 is applied to a LED lighting device with high luminance or high power, the wiring terminals and the electric wires must possess high current durability and high manufacturing cost. More disadvantageously, the lamp currents Io1, Io2, I03 will be relatively high. This would deteriorate the power loss and lower the overall power efficiency.